The Geographic Information System-based flood damage simulation model HOWAD

The Geographic Information System (GIS)-based flood damage simulation model HOWAD for buildings and land-use units is dealing with a new high-resolution approach. Spatially, it interlinks water depths from hydrodynamic modelling, accurate geographic data for buildings and land-use units, and a building typology based on urban structure types. For calculations of the potential physical and monetary damage to residential buildings, detailed synthetic depth-damage functions for each building type are used that are based on civil engineering analyses of the building constructions. Damage modelling for other land-use types like commercial, industrial or agricultural properties up to now is based on individual expert estimates. The application of the object-based approach with a high spatial and contextual resolution allows not only a detailed assessment of impacts due to the current flood hazard but also the simulation of future risks under the conditions of climate and societal change. In addition, the method enables ex-ante analyses of effects of risk reduction measures and thus the comparison of decision alternatives. The monetary damage for individual buildings and land-use units can be aggregated on different scales (administrative districts, catchment areas, etc.). The strength of the approach is a highly reliable methodology especially for housing areas using synthetic depth-damage functions based on the calculation of refurbishment costs for potential inundation depths. The applicability of the model HOWAD is demonstrated by results from a case study on the German Elbe River floodplain.